The invention relates to a method for filling a tube with a paste, ointment, gel or cream, the tube consisting of a tubular or conical casing of flexible material, having a closable filling orifice at one end and being closed at the opposite end to the filling orifice, the filling orifice being flattened at least in its edge region once the paste, ointment, cream or gel has been introduced, the internal volume of the tube being reduced by means of a die that deforms the casing and the filling orifice being closed.
The invention relates, in particular, to the filling of aluminum or laminate tubes with products which are capable of oxidizing in air, for example oxidative coloring creams for coloring hair in hair cosmetology. It is known to fill a coloring cream tube of this type in a plurality of steps. Nitrogen gas is initially introduced into the empty tube. The coloring cream is then introduced from bottom to top, in other words beginning with the still closed end of the tube. After introducing further nitrogen gas, the filling orifice is flattened and folded by closing two folding jaws. The folding process takes place in a known manner. To prevent the subsequent penetration of air, an annular latex film or a heat sealing lacquer is applied internally to the tube end. When the tube is closed, the filling orifice is initially flattened so the latex-coated internal regions of the filling orifice rest against one another and form a gas-tight seal after compression. When heat sealing lacquer is used, the lacquer is melted by heating jaws and the hermetic seal achieved in this way.
In practice, it is impossible to prevent a relatively large space filled predominantly with nitrogen gas from remaining between the content of the tube, i.e. the coloring cream in the specific case, and the closure of the filling orifice. However, this space still contains sufficient atmospheric oxygen to oxidize and therefore discolor the exposed surface of the coloring cream facing the filling orifice, over the course of time. The user will then observe undesirable discoloration and streaks when the coloring cream is squeezed out.
The method of the type mentioned at the outset is known from German Utility Model DE 87 08 939 U1. In that case, the amount of residual air remaining in a bag for a medical infusion liquid after closure of the container is to be substantially reduced. Once the container consisting of plastics material has been filled, the size of the filling orifice is reduced by a first welding process. The filling level is then raised into the filling nozzle by elastic deformation of the container. In the process, a die integrated in the blow mould for the plastic bottle is pressed against the main part of the container casing which is arranged remotely from the filling orifice and below the filling level of the infusion liquid. Finally, the mouth of the filling nozzle remaining after the first welding process is welded in a second welding process.
A drawback of this known method is the requisite expenditure which is manifested, on the one hand, by the number of steps of the method. Three steps are required, namely a first welding process, elastic deformation of the container and finally a second welding process. Complex modification of the filling device is also required. A separate die with an actuating element and a corresponding drive has to be installed in the holder or in the blow mould. Finally, a control means for the die drive has to be fitted to maintain predetermined deformation of the container. In fact, if the container is excessively deformed, the content of the container is squeezed out of the filling orifice and this results in corresponding soiling of the tube filling facility and difficulty in welding the filling nozzle which has been wetted by the product in its interior.
It is accordingly the object of the invention to develop the method of the type mentioned at the outset so as to considerably reduce the volume of the gas-filled space remaining in the closed tube, in a cost-effective, simple and unproblematic manner, necessitating minimal modification of the filling facility and no change to the filling method or the tube.
This object is achieved according to the invention by the method mentioned at the outset in that the internal volume of the tube is reduced simultaneously with the flattening and closure of the filling orifice. According to the invention the internal volume of the tube is reduced not between two welding processes as in the method according to DE 87 08 939 U1, but simultaneously with the flattening and closure of the filling orifice. Instead of three steps during closure of the container according to the prior art, only a single step is required according to the invention.
In particular, it is proposed to reduce the internal volume of the tube by pressing a triangular region of the casing, adjoining the filling orifice against the opposite side of the casing, the vertex of the triangle pointing toward the closed end of the tube. The container is deformed substantially in the region above the product, in other words in the region of the gas content. The deformation provided according to the invention may be retained after final closure of the tube as it corresponds exactly to the transition from the cylindrical part of the filled tube to the flat region and therefore does not impair the aesthetic appearance and is relatively unnoticeable.
To make the tube particularly impermeable to air and, in particular, to atmospheric oxygen, it is also proposed that the tube consists of metal, in particular of aluminum, in a manner known per se.
It is also advantageous to use tubes having an annular film of latex or the like on the interior of the filling orifice. After being folded and welded, tubes of this type are particularly airtight in the region of the fold.
The invention also relates to a device for carrying out the method according to the invention, comprising two opposing clinching jaws which can be moved toward or away from one another. These clinching jaws have the function of flattening and folding the filling orifice of the tube.
The above-mentioned object of the invention is achieved here in that a die is mounted on one clinching jaw and a plate-shaped counterpart on the other clinching jaw. If the clinching jaws move toward one another during closure of the tube, the casing limiting the gas-filled space of the tube is thus squeezed at the same time to a predetermined extent, the residual gas content being considerably reduced. A separate step and an expensive control means for the deformation of the container is not required according to the invention.
It is also proposed that the die has the form of a triangular plate, the vertex of the triangle pointing away from one clinching jaw. The advantages of the resultant triangular deformation have been mentioned hereinbefore.
Existing facilities may be converted in a particularly simple, unproblematic and cost-effective manner if the die and the counterpart are fixed directly and rigidly to the respective clinching jaw according to a further embodiment of the invention. It is particularly clear here that, according to the invention, the flattening of the filling orifice reduces the volume of the region of the tube containing the residual gas.
It is also proposed that the pressing face of the die is arranged substantially parallel to the longitudinal axis of the device and the pressing face of the counterpart is arranged obliquely outwardly from this longitudinal axis. The longitudinal axis of the device is determined by the longitudinal axis of the tube. In this embodiment, the counterpart prevents damage to the front of the tube which rests thereon and generally carries an inscription.
Finally, it is proposed that the arms of the counterpart and of the die are arranged at right angles to one another. However, the arms may be arranged at an acute angle of up to 45xc2x0 to one another. The angles of the counterpart and the die are not generally identical, the die being at a right angle and the counterpart at a smaller angle.